Apologies to those of you ‘in the know’. You’ve probably not had any trouble. Some of us, however, have had one or two ‘problems’ with size since we started printing, so perhaps now would be a good time to address the issue of size. It seems to be almost as contentious an issue as colour!
There are two elements to size when working with images on the computer. One is actual size – eg 10 x 8 cms. The other is resolution – how many dots per inch (dpi). Dpi is also sometimes described as pixels per inch, or per centimetre. You can usually choose which you use in your software. Dpi is the most common, and is what is used on our web site, so that’s what I’m going to use here.
Just in case you’re not sure, dpi tells you how detailed an image is. If you compare these two images, it’s easy to see that an image with a higher number of dots per inch is going to be able to show more detail than one with a lower number of dots per inch
Size and resolution are sometimes connected – if you change one, the other will change too. If you make an image bigger, the number of dots per inch will be smaller, and vice versa. In some software, eg Paint.net, it’s possible to change one whilst keeping the other the same. This can be particularly useful if you have a large design (perhaps hand-drawn) which you want to make smaller.
I think the thing which is possibly most confusing (because we don’t think about it and are easily convinced by what we see) is that what you see on your screen is usually not what you are going to get. If you are working on a small design, you probably zoom in, to make it easier to see what you’re doing. If you are working on a large design, you may make it smaller, so that you get the whole picture on your screen. It doesn’t help that, often when you change the size of an image, the image on the screen doesn’t actually change. What changes is the ruler along the edge! It’s therefore very easy to forget what the actual size is. You upload it to the web site and suddenly, the size is all wrong!
Sometimes, of course, you upload a design and then decide it would look better at a different size. You can change the size on the web site by clicking on the ‘larger’ and ‘smaller’ buttons. When you upload your design it will show at the 150dpi size, which might mean that it is not the size you planned. Click on the smaller button till the number of dots is showing what you had in your design. Eg, if you upload a design at 200 dpi, it will look bigger than you expected. Click on the smaller button until the number gets to 200. Your design should then be the right size.
If, however, you have decided that you want it at a different size, you can also use the buttons to change the size. You can’t make a design bigger than the one you upload, because it quite possibly won’t print very well. If you want it bigger, you will have to work on it offline, and upload the altered design.
The left-hand circle below is printed at an acceptable resolution. The right-hand circle has been enlarged, making the dpi too low. You can see that the edge of the circle is blurred. This would not print nicely.
Although, initially, we said that our printer preferred 200 – 300 dpi, it seems that that information was wrong. It seems happiest at 150 – 200 dpi.
I hope this helps a bit. It seems complicated, written down. I apologise if my explanations confuse you more! After a while, it does seem to make more sense! However, if you're still having difficulties, either because you can't quite understand resolution and size, or because the web site can't understand you (it's not unknown for the web site to throw a wobbly and apparently do it's own thing!) then please do get in touch (or via Facebook), and we will do our best to help you.
There's a second post about size - Does size still matter? - here.